The present invention relates to a differential control unit for front and rear wheels of a 4-wheel drive vehicle which is disposed on a propeller shaft for connecting a transmission and a differential gear of the 4-wheel drive vehicle so as to improve driving performance and keep the vehicle stable by absorbing and controlling the speed difference generated between the front and rear wheels and by limiting the torsion stress when turning.
In general, because speed difference is generated between front wheels and rear wheels when turning the 4-wheel drive vehicle, it causes relative spin in the wheels and torsion in the driving system so that it affects driving performance.
A specific tight corner braking phenomena occurs in the 4-wheel drive vehicle due to a difference of radius of gyration between the front and rear wheels, and more particularly due to the difference of the number of rotations according to the big radius of gyration for the front wheel and the small radius of gyration for the rear wheel when turning the vehicle.
The difference of radius of gyration causes forced slipping of the wheels or torsion stress of the driving system in parts like the propeller shaft. This results in locking the driving system and thereby braking the vehicle.
The braking phenomena of the driving system has a harmful influence upon rigidity of the propeller shaft and also on smooth turning of the vehicle, and causes loss of power.
As the propeller shaft of the 4-wheel drive vehicle is a direct connecting type, the rear wheels having small rotative velocity slip because of the speed difference between the front and rear wheels when turning the vehicle. Accordingly, driving performance and stability of the vehicle drops.
In addition, because torsion stress occurs while turning the vehicle causing the vehicle body to vibrate, when designing the vehicle, the size and weight of the propeller shaft should be increased to reduce vibration.
In recent years, a viscose coupling has been used to solve the problem. However, the viscose coupling has a complex structure and increases manufacturing costs.